Method of and apparatus for testing relays



April 11, 1939. R H E TE 2 ,154,379

. METHOD OF AND APPARATUS FOR TESTING RELAYS Fild' May 25, 1936 I N m w. k a:

OPERATING TIME . INVENTOR P. H. ESTES -3i BY A ORNEY v Patented Apr. 11, 1939 I UNITED STATES or AND mans'rus' FOR. TESTING RELAYS Mn'riron PATENT OFFICE Phillip n. Estes, Rutherford, IN. 1., assignor to The Western Union Telegraph Company, New York, N. Y-ya corporation oi-New York Application Ma, 23, 1936, S erial No. 81,530

her to facilitate the proper adjustment of the relay. The present application is, directed to an improvement or modification of the method and apparatus broadly claimed in the copending application of W. D. Buckingham, Ser. No. 81,499, filed May 23, 1936. A large number o'f relays are employed in signalling and communication systems and the operation of thesystems depends upon the proper functioning of the individual relays. As an example, in multiplex and simplex telegraph systems for high speed telegraph communication, the operation of the systems depends upon the correct functioning of polarized repeating or line relays. These relays which may, for example, be of the type'disclosed in the patents to William Finn, No. 1,160,097, dated November 9. 1915, or Reissue 14,304, dated May 22,1917, must be so adjusted that they are not biased, that thetravel time of the armature between contacts is between certain limits and contact chatter or bounce is substantially eliminated in order that the system may operate reliably at high speeds. Since the transmission depends upon the operative characteristics of these relays, each re- 30 necessary to maintain the system in operation:

In general terms the object of this invention is to provide an improved and simplified method of testing relays, including polarized and neutral relays, in order that the same may be adjusted to obtain the desired operating characteristics.

A further object of the invention is to arrange a cathode ray oscillograph to indicate one or more of the following characteristics of the relay: first, the travel time of the armature between contacts; second, the number and character of the contact bounces as the armature engages eachcontact; third, the firmness of con-.-

tact between movable and, stationary contacts of the relay as affected by the surface of the contacts and freedom from dirt: fourth the existence of mechanical or electrical bias in the relay} fifth, the equality or lack of equality of contact 'time on opposite contacts; sixth, the operating" Other objects and advantages of the invention 55 will appear from the following descriptionof the lay must be tested frequently and readjusted if llclaims. (01. 175-183) embodiments thereof shown in "the accompanying drawing, wherein:

Fig. In: a circuit diagram of testapparatus embodying the invention;

Fig. 2 is a similar diagram of a modification: and

Figs. 3, 4 and 5 are'graphs. of the traces-obtained by the oscillograph ina test set arranged as shown. in Fig. 2.

Referring to Fig. 1, the relay 10 under test is shownlas comprising two operating windings ll and a movable armature l2adapted to engage stationary contacts l3 and M, respectively. While the invention may be utilized in connection with various-types of relays, the relay iii may be assumed-to be'a' polarized-relayrhaving differential or opposing windingswhich i'orlthe purposes of the test'are connected in series to a source of periodically varying current represented by the" transformer supplied with sixty-cycle sinusoidal alternating'current. The ordinary polarized line relay extensively used in high'speed telegraph systems is adapted to respond to signals of a frequency of the order of sixty cycles or, from about twenty to one able operating voltages may be employed as will be a parent to-those skilled in the art and in the case of neutral relays, a switch 16 may be provided to connect a battery I! in series with the transformer l5 and the operating coils of the relay. If the potential of the battery I 1 is approximately equal to the peak voltage derived from the transformer i 5, a neutral relay connected in series relation therewith will-be energized and deenergized at a rate dependent upon the frequency of the alternating current source.

19 are further provided to impress direct-current potentials ofopposite polarity upon the contacts l3 and Hi. The potential of each of. the batteries is sufficient to produce an appreciable deflection of the beam of a cathode ray tube.

The operating characteristics of the relay Ill including contact chatter are determined by utilizing a cathode ray oscillograph 25. The cath- In the system shown, batteries l8 and ode ray oscillograph illustrated is of a conventional type and comprises a heated cathode :25, an anode 27, a pair of plates 28 for producing a sweep of the electron beam and a pair of deflec tion plates 29 at right angles to the sweep plates 23 for deflecting the beam in accordance with the operation of the relay under test. The electron beam impinges upon a luminescent screen 30 formed on or adjacent the upper end of the cathode ray tube to form a visible trace representing the movements of the electron beam as it is deflected by the sweep plates 28 and the deflection plates it. Operating potentials for the cathode 2t and the anode 27 are supplied through the conductors iii in the usual manner. While an oscillograph of conventional type is illustrated for the purpose of explaining the intion between the potential applied to the relay it t and that impressed upon the sweep plates 26. Either the resistor 32.? or the condenser 33 may be adjustable'in order to vary the phase relation between said circuits or these elements of the circuit may be omitted in case no phase adjustment is required. The deflection plates 29 are connected to the terminals of a resistor 3% which may be adjustable if desired. The resistor 34 is connected in series relation with the armature l2 and with the battery it or l9 depending upon whether the armature l2'is in engagement with the contact I3 or E i, and thus the potential between the deflection plates 29 is reversed as the armature engages first one and then the other of the relay contacts l3 and M.

The trace or pattern obtained upon the screen portion of the cathode ray tube as the relay Ill operates in response to the alternating current applied to the relay windings is shown for an assumed operating condition in Fig. 1. When zero or equal potentials are applied to the pair of sweep plates 28 and to the pair of deflection plates 29, the cathode ray beam remains stationary and impinges upon the center of the screen 30. The alternating potentialapplied to the sweep plates 28 from the supply circuit deflects the cathode ray beam alternately in the directions indicated by the arrows 36 along the central axis 31 of the screen. The potentials applied to the rear deflection plate 29 with respect to the grounded front plate as the relay armature l2 engages the stationary relay contacts I3 and M, respectively, deflects the cathode ray beam at right angles to the axis 37 thereby forming the trace 38 while the armature His in engagement with one contact and thetrace 39 while the armature I2 is in engagement with the other contact; The trace tflupon the screen of the cathode ray tube is formed while the armature is travelling between the respective relay contacts, the portion of the trace to the left of the center of the screen being formed while the armature is travelling in one direction and that to the right while the armature'is travelling in the opposite direction.

arc ers If there is contact chatter when the relay armature engages one or the other or the contacts,

one or more dots il, 62 are formed upon the screen 3G indicating the number and duration of the contact bounces. Thus the pattern produced by the movement of the cathode ray beam in- 1. dicates the travel time of the relay armature and the character and severity of the contact chatter, if any. The pattern will also be affected if the contact between the armature and one of the relay contacts is imperfect/to such an extent as to afiect the contact resistance. materially as a decrease in the normal current traversing the relay contacts will 'alter the potential drop in the resistor 36.

In Fig. 2 is shown a modification in which the deflection plates 29 are subjected to the alternating sinusoidal potential of the supply circuit in addition to the potential of the batteries is and it associated with the relay contacts. order to effect this result, the armature l2 and resistor Stare connected in series relation with the secondary winding of the transformer i5 whereby when the circuit of the battery 58 or it is closed through the relay armature l2, the deflecting potential applied'to the deflection plates 28 consists of the potential of said battery plus that existing across the terminals of the second ary winding of the transformer.

The circuit of the sweep plates 2% further coniprlses a potentiometer 55 to permit adjustment of the extent of sweep oi the cathode ray beam. A switch or key it is also provided in the circuit of the condenser 33 in order to permit the oper 'ation of the test set with the potentials applied to the relay windings and to the sweep plates 28 in phase.

As shown in the diagram upon the screen portion of the cathode ray tube, a different pattern is obtained in this case. Then the relay armature is travelling from one contact to the other, the traces til on the axis 3?,of the screen are obtained as in the modification of Fig. 1. If there is any contact chatter, this is indicated by the dots M and t2 as in Fig. 1'. However, the trace formed during the interval when the armature is in engagement with one or the other of the relay contacts is arcuate in shape as indicated at 50 and iii and may contain dots 52 and 53 representing contact chatter.

In the pattern shown in Fig. 2, the ends of the arcuate traces 59 and El overlap and the inner ends of the traces id are separated by a gap. Such a pattern indicates that the sweep of the beam starts before the relay armature i2 commences to move away from the stationary contact l3 or M. In order to bring the sweep of the beam of the cathode ray tube in phase with the movement of the armature of the relay under test, the adjustment of the resistor 321s changed until the gap between the traces 40 is substantially eliminated thereby obtaining the pattern shown in Fig. 3. This pattern, however, is unsymmetrical with respect to the axis of the screen of the cathode ray tube, indicating that the relay is mechanically d'r electrically biased. After the relay is adjusted to eliminate this bias, the symmetrical pattern of Fig. 4 is obtained. The relay -may also be adjusted to eliminate the contact axis of the screen to end ofthe trace l represents the operating time of the relay; 1. e. the

time elapsing between the'beginning' oi the cyclev of the alternating potential irom the source connected to the relay windings and the engagement oi. the armature with one of its contacts in reto the energization of the relay. If the frequency of the alternating potential is known and the potential is sinusoidal, the operating time may be readily determined in .hundredths of a 1 second.

The invention is not limited to the particular 1 embodiments disclosed herein for purposes of ii- I lustration as such embodiments may be modified without departing from the scope of the invention as defined in the appended claims. No claim is spectively, and deflecting the beam of the oscillograph laterally oi the sweep movement in accordance with the position of the relay armature and with one of said alternating potentials.

2. The -method of testing a: contact-making relay with a. cathode ray oscillograph having sweep plates and deflection plates which comprises impressing alternatingsubstantially sinusoidal potentials oi! the same frequency upon the relay and the sweep plates of the oscillograph respectively, and deflecting the beam of the oscillograph laterally of thesweep movement in accordance with the opening and closing of the relay contacts and with-one of said alternating potentials.

3. The method of testing a movable-armature relay with a cathode ray oscillograph having sweep plates and deflection plates which comprises periodically energizing said relay and the sweep plates oithe oscillograph and deflecting thebeain oi the oscillographlaterally of the sweep movement in accordance with the potential applied to said relay and with the movement of the relay armature.

4. Apparatus ior testing relays provided with contacts comprising a cathode ray oscillograph having sweep plates and deflection plates, means including a source of current for periodically energizing the relay under test and the sweep plates of said oscillograph, a second source of r current, a-conn'ection from said second source of current through a contact of said relay to the deflection plates of the oscillograph and means for further controlling the potential impressed,

upon said deflection plates in accordance with the relay-operating potential.

5. Apparatus for testing relays provided with contacts comprising amathode ray oscillograph having sweep plates and deflection plates, means 06 including a source of current {or periodically energizing the relay under test and the sweep plates or said oscillograph, means for impressing diflersaid relay to the deflection plates of the oscilloraph and means for further controlling the potential impressed upon'said deflection plates in accordance with the relay operating potential.

6. Apparatus for testing relays provided with contacts comprising a cathoderay oscillograph having sweep plates and deflection plates, a source of alternating current connected to the relay under test and to said sweep plates, a secand source of current, a resistor connected in series relation with both said sources of current and with a contact of said relay and connections from the terminals of said resistor to the deflection plates of the oscillograph.

7. Apparatus for indicating contact chatter in a relay comprising acathode ray oscillograph having means for producing and deflecting a H beam of electrons, a source of alternating current connected to the relay and means for impressing upon the deflecting means of the oscillograph a potential varying with the relay operating potential and the open and closed condition of the relay contacts.

8. Apparatus for testing relays provided with contacts comprising a cathode ray oscillograph having sweep plates and deflection plates, means ior applying alternating potentials to the relay under test and said sweep plates, respectively, means for varying the phase relation of said potentials and means including a contact of the relay for varying the potential impressed upon said deflection plates as the relay operates.

9. Apparatus for testing relays provided with contacts comprising a cathode ray oscillograph having sweep plates and deflection plates, a

source of alternating current, circuits connecting said source to the relay under test and to said sweep plates, respectively, phase shifting means in one of said circuits, a source of current connected to one oi the contacts'oi' said relay, and a connection from another relay contact to one of said deflection plates of the oscillograph.

10. Apparatus ior testing relays comprising a cathode ray oscillograph having sweep plates and deflection plates, a common source of potential for the relay under test and the sweep plates of said' oscillograph, connections between said source and the relay and sweep plates, respectively, phase adjusting'means in one of said connections and a connection. between a contact of the relay and one of the deflection plates of the oscillograph.

'11. Apparatus for testing relays comprising a cathode ray oscillograph having sweep plates and deflection plates, means for energizing the sweep plates of the oscillograph concurrently with the operation of the relay under test, means for altering the potential of the deflecting plates of the oscillograph as the relay armature moves, phase shifting meansior varying the phase relation between the potentials applied to the sweep plates of the oscillograph and to the relay, respectively, and a switch arranged to control said phase shifting means.

PHIILIP H. ESTES. 

